I don't think SF2 import currently supports more than 128 banks - or rather, anything above bank 128 is simply mapped as a "drums" bank.

I'm not referring to banks above 128. I'm referring to Bank 16 and Bank 17. And yes, the Bank 3 Nyctophobia import worked (among others). It's for these specific variations that it's failing on.

Technically SF2 can do MSB and LSB if you use all 16 bits of the wBank value, but no SF2 editor has support for that yet, and the bank I'm using doesn't do that. All that happened in the SF2 import is a booboo with MIDI import. The entire SF2 is read properly by the Add Sound Bank and Import MIDI Library, it's just that in this one small case it fails to import something that it otherwise would fail on. I've proven before that SF2 import is not GM-only.

The problem here is that the MIDI file in question also sets a non-zero bank LSB, so OpenMPT cannot find the correct bank in the file. I suppose at least for SF2 files we could fall back to ignoring the LSB when trying to find a suitable instrument. Not sure if it would be the right thing to do with DLS banks.

Considering that SF2 has wBank as a 16 bit ripe for expansion into MSB+LSB like me and a friend are working, that ignore setting should be a toggle. But otherwise that's a good idea.

Do you mean that the upper 8 bits of the wBank value would be used for the LSB then (i.e. MSB and LSB are swapped)? If so, support for that would have to be added in OpenMPT first anyway.

Implemented in r17809. Note that a perfect MSB+LSB match is still preferred over just a s MSB match.